If the pedal is going to the floor you have a leak somewhere and air in the system. The fluid in the hydraulic system does not compress noticeably when set up correctly.

I suggest you check the seals on the callipers and also the master cylinder.

If the pedal stays hard then the type and condition of the pads and disks will affect the braking performance. Good disks and good quality pad will work best in most conditions even if the disk is on the hot side.

Disks, callipers and pads can be bought for reasonable sums of a popular auction site or good motor factors.

I have just done an overhaul on a 406 and the overall cost was reasonable. Cleaning up the ABS sensors also cured my intermittent ABS fault.

I doubt that there is any air in the system as I have just bled over a litre of fluid through the system to swap the fluid and she has recently had discs and pads hence why I'm a bit puddled also the fluid level is staying the same so no leak. I don't get brake fade so the pads n discs are reasonable quality just stumped with poor performance of the brakes

I'll try to make a video showing how the pedal is moving down after initially coming to an halt on mine. The effect is actually quite severe, just did some testing before I started my drive home from work.

Ok so just got back from kwik split and after a good check of the system with all wheels off and micrometers etc etc the official diagnosis is " I'm sorry sir but you have been driving a car with a far superior braking system than your peugeot!" Hhhmmmm they also told me that high pressure diesels can have brake peddle creep! I find this a bit strange but slightly reassuring and after popping to shops etc the 407 and a bit of running around the brakes feel fine again I suppose its all in my head. Still a bit concerned over the brake peddle creep David is this something I should be concerned about do u think? Anyway if anything else appears ill let you all know.Black MI16how did you get on with asking the your local strealers about your peddle creep?

My 407s brake pedal will creep right down to the floor if you maintain the pressure but once the engine is turned off and i've pressed the pedal a few times to release the vacuum it goes solid with no creep.
another 407 hdi i've driven and my dads vivaro do exactly the same.
all i've checked for leaks and the brake fluid is clean with none of the telltale black shite in the reservoir.

my 407 has done it as long as i had it and the vivaro has always done it from new.